Seizures in Glioblastoma: Why They Happen, Which Types Are Most Common, and How Medication and Safety Strategies Help
A seizure is often how glioblastoma announces itself. For roughly one in three newly diagnosed patients, it is the event that leads to the emergency MRI and diagnosis. Even if your diagnosis came another way, seizures remain a real possibility at any stage of the illness. They are frightening - especially when they arrive without warning - but they are manageable with the right medication, daily habits, and a care team that knows neuro-oncology.
This guide explains why glioblastoma causes seizures, describes the types you are most likely to encounter, shows how anti-seizure medication is chosen, and offers practical safety guidance for daily life. If you are newly diagnosed and building your overall treatment plan, the guide on what to prioritize in the first 30 days after a glioblastoma diagnosis covers the bigger picture.
Why does glioblastoma cause seizures?
Glioblastoma causes seizures by releasing excess glutamate - the brain's main excitatory chemical - into nearby tissue, blocking the brain's natural calming signals, and creating electrical instability through swelling and pressure. These combined effects make neurons fire in uncontrolled bursts, producing a seizure.
The primary driver is a molecular transporter called system xc-. Glioblastoma cells use it continuously, pumping glutamate out of the tumor and into the fluid around healthy neurons. Normal neurons cannot handle that level of stimulation. They fire repeatedly, and those patterns can spread across the cortex. Research on how glutamate works in glioblastoma shows how this glutamate release drives both tumor growth and seizure generation through the same process - the same biology that makes glioblastoma aggressive also makes it prone to causing seizures.
A second factor is the suppression of GABA, the brain's primary inhibitory neurotransmitter. Glioblastoma disrupts GABA signals in the tissue surrounding it. Without adequate inhibition, the brain loses its normal electrical braking mechanism. Neurons fire more easily and recover more slowly.
Peritumoral edema - the swelling around the tumor - adds further instability. Swelling compresses healthy tissue, alters the balance of ions across cell membranes, and lowers the seizure threshold in ways that extend well beyond the tumor itself. This is one reason treating the edema - most often with the steroid dexamethasone - sometimes reduces seizure frequency, and one reason surgical removal of the tumor can improve seizure control even before anti-seizure drugs are started.
How common are seizures in glioblastoma?
Between 30% and 50% of people with glioblastoma will experience at least one seizure during their illness, according to a review of seizure management in patients with brain tumors. For a substantial number of those patients, the seizure is the first visible symptom - the event that sends them to the emergency department and leads to the diagnosis.
Seizure rates in glioblastoma (IDH-wildtype, grade 4) are actually somewhat lower than in lower-grade gliomas. IDH-mutant tumors grow slowly in the cortex for years, building up electrical irritability over time. Glioblastoma grows faster and spreads more diffusely. Still, the rate is high enough that every patient and caregiver should understand what seizures look like and what to do when one happens.
One important point: a new or changed seizure does not automatically mean the tumor has progressed. Breakthrough seizures can happen because of a missed medication dose, an infection, a fever, sleep deprivation, or an electrolyte imbalance. Your neuro-oncology team will investigate the cause before deciding if the disease got worse.
What types of seizures does glioblastoma cause?
The type of seizure depends on where in the brain the abnormal electrical activity starts and how far it spreads. Glioblastoma can produce any of the following types, and some patients experience more than one.
Focal aware seizures
In a focal aware seizure, the person stays conscious and can often describe what they feel. Common experiences include tingling or rhythmic twitching in one hand or arm, brief visual disturbances, an unusual smell or taste, a sudden strong sense of deja vu, or a wave of unexplained anxiety. These episodes are often brief - sometimes only seconds - and can be easy to dismiss as anxiety or a strange passing feeling. They should not be dismissed.
Focal impaired awareness seizures
Here, awareness is partially or fully reduced for a brief period. The person may stare blankly, make repetitive movements such as lip smacking or hand rubbing, and appear unresponsive to questions or touch. After the seizure ends, there is typically a period of confusion called the postictal state. The person may have no memory of what happened.
Tonic-clonic seizures
These involve a stiffening phase followed by rhythmic, forceful jerking of the limbs, with complete loss of consciousness. They can include loss of bladder control. They are the type most people picture when they think of a seizure, and they frighten those watching. Most last under two minutes and stop on their own. A tonic-clonic seizure that continues beyond five minutes requires emergency care.
Secondary generalization
A focal seizure can spread from where it starts to involve both halves of the brain, becoming generalized. What begins as twitching in one hand may escalate into a full tonic-clonic event within seconds. Secondary generalization is common in glioblastoma and is why early anti-seizure treatment matters - controlling the initial focal activity reduces the risk of dangerous escalation.
Which anti-seizure medications are used in glioblastoma?
After a confirmed seizure, anti-seizure medication - also called an antiepileptic drug, or AED - is started. In glioblastoma, the choice of medication matters more than in most other seizure settings, because of how certain AEDs interact with temozolomide chemotherapy and the corticosteroid dexamethasone.
Older AEDs such as phenytoin and carbamazepine are enzyme inducers: they activate liver enzymes that break down other drugs more rapidly. This reduces how much temozolomide stays in your blood, potentially weakening the chemotherapy effect. They also change how dexamethasone works. For these reasons, doctors generally avoid enzyme-inducing AEDs in glioblastoma, and most neuro-oncology centers have moved away from them in recent years.
The most widely prescribed first-line medication is levetiracetam (marketed as Keppra). A 2025 review of levetiracetam and valproic acid use in glioma confirmed that levetiracetam does not induce liver enzymes, does not meaningfully interfere with temozolomide, and provides steady seizure control in glioma patients. You can get it as a tablet, oral liquid, or intravenous form - the IV form is particularly useful after surgery when people can't swallow. The most common side effects are irritability, mood changes, and fatigue. Some patients experience more serious psychiatric symptoms, which you should discuss promptly with your doctor.
Valproic acid is a second widely used option. It does not induce liver enzymes, and some studies suggest it may have a modest anti-tumor effect by affecting how genes work. Consistent clinical proof of a survival benefit has not yet emerged, but it remains a reasonable alternative - particularly for patients who cannot tolerate levetiracetam. Your doctor will need to monitor your blood cell counts and liver function, especially alongside temozolomide.
Other options that may be considered when first-line drugs don't work or you can't take them include lacosamide, lamotrigine, brivaracetam, and perampanel. Perampanel is worth noting in this context: it blocks AMPA-type glutamate receptors, directly targeting the same glutamate pathway that glioblastoma exploits to generate seizures in surrounding tissue.
Current guidelines from the Society for Neuro-Oncology and the European Association for Neuro-Oncology make clear that prophylactic anti-seizure medication shouldn't start before your first seizure. Clinical trials have consistently found that pre-emptive AED treatment does not reduce the risk of a first seizure, and the side effects are real. Medication begins after a documented seizure, not in anticipation of one.
AEDs can produce cognitive side effects, including slowed processing, memory difficulties, and fatigue. These effects can overlap with the cognitive consequences of the tumor itself, radiation, and temozolomide, so it's hard to know what's causing the changes. If you are managing significant cognitive changes, the article on chemo brain and cognitive changes during glioblastoma treatment explains how to tell the causes apart and what steps are available.
Drug interactions also extend to herbal supplements and over-the-counter products. Some commonly used supplements may affect how AEDs or chemotherapy work. For a detailed review, see the guide to safe supplement use alongside temozolomide chemotherapy.
Safety strategies at home and in daily life
A seizure in the wrong setting can cause more harm than the seizure itself. The goal of daily safety planning is to reduce the specific risks that matter most while maintaining your quality of life.
Driving
This is the most important restriction. Driving laws vary by country, but most require a documented seizure-free period before you can drive again - commonly 6 to 12 months. In many jurisdictions, doctors must tell the licensing authority. Do not drive until your neurologist explicitly clears you. This applies even if your seizures feel mild or brief, and whether or not you're alert between them.
Heights and machinery
Avoid ladders, scaffolding, and unguarded heights. If your work involves operating heavy machinery or working at elevation, you should discuss modifications with your employer. A seizure during these activities puts you at risk of serious injury or harm to others nearby.
Water safety
Do not swim alone. A seizure in or near water carries a real drowning risk, even in shallow depths. Showers are generally safer than baths. If you prefer baths, keep the water level low, do not lock the door, and make sure someone nearby knows you are bathing.
Cooking and household hazards
Use back burners when possible and turn pot handles inward so they cannot be knocked. Induction cooktops turn off automatically to reduce burn risk. Non-slip mats in the bathroom and grab rails near the toilet and shower reduce injury if you fall. A medical alert identification - a bracelet, wallet card, or phone lock-screen notification - ensures first responders can see your diagnosis and medications if you can't tell them.
Medication adherence
Missed doses are among the most common triggers for breakthrough seizures. A weekly pill organizer, phone reminders set to a consistent time, and a household member who knows your schedule all reduce this preventable risk. If you are traveling internationally, carry enough medication for your full trip plus a few extra days, in your carry-on luggage, never in checked baggage.
What to do when a seizure happens
Having a clear plan reduces the time it takes to act correctly. The CDC's guidance on seizure first aid outlines the essential steps:
Keep the person safe. Move hard or sharp objects away from them.
Gently guide them to the floor if they are not already there, and turn them onto their side. This keeps the airway clear.
Do not put anything in their mouth. The idea that a person can swallow their tongue during a seizure is a persistent myth. Objects placed in the mouth cause injury, not protection.
Time the seizure from the moment it begins. This information matters to the treating team.
Stay with them until they are fully awake and oriented to their surroundings.
Expect confusion, fatigue, and sometimes a headache in the minutes following the seizure. This postictal phase is normal and may last 15 to 30 minutes.
Call emergency services if the seizure lasts more than five minutes, if the person doesn't wake up, if one seizure follows immediately after another without a recovery period, if the person is injured during the episode, or if this is the first time you have witnessed this patient have a seizure.
Some patients who have previously had prolonged seizures get a rescue medication - typically a benzodiazepine in nasal spray or buccal gel form - to use at home if a seizure does not stop within an agreed time. Ask your neuro-oncology team whether a written rescue plan is appropriate for your situation, and make sure the primary caregiver knows exactly when and how to use it.
Status epilepticus - a seizure lasting more than five minutes, or multiple seizures without full recovery between them - is a medical emergency. Do not wait to see if it resolves. Call emergency services immediately.
When to talk to your doctor
Talk to your neuro-oncologist or neurologist if you experience a first seizure at any point in your illness; if your seizures change in character, frequency, or duration; if your anti-seizure medication causes mood changes, cognitive effects, or other side effects that affect daily function; if you experienced an episode you are unsure was a seizure; or if you are planning travel and need guidance on medication supply, local emergency care, or driving rules in another country.
Seizure management in glioblastoma is an ongoing process, not a one-time decision. As tumor biology and treatment change, medication may need adjusting. Keep your full care team closely informed of any changes in seizure pattern.
If you are weighing treatment options internationally or seeking an expert second opinion on your overall glioblastoma care plan - including symptom and seizure management - you can upload your medical records and scan findings for a remote expert review through HealthUnwired, with a response typically available within 48 hours.
This article is for general information and is not a substitute for medical advice. Always consult your oncologist or care team about your specific situation.